[Mac] Fix "Pressing ESC does not cancel in-progress tab drag"	
[Mac] Fix "Pressing ESC does not cancel in-progress tab drag"	

This matches Chrome's behavior on Windows and corresponds to how users expect a drag to behave.

BUG=78437
TEST=1. Start a tab drag within the tab-strip without detaching. Press ESC. Tab should revert to its original position. 2. Start a tab drag that detaches the tab from a window that has multiple tabs. Press ESC. Tab should revert to its original location in its previous window. 3. Start a tab drag of a tab from a single-tab window. Press ESC. The drag should be reverted.

Review URL: http://codereview.chromium.org/6840032

git-svn-id: http://src.chromium.org/svn/trunk/src@81592 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: c6a475d6205894caa023e88e5a78fbd1d5914234
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser